1. Field of the Invention
The present invention relates to a gas discharge tube; and, in particular, to a gas discharge tube for use as a light source for a spectroscope, chromatography, or the like.
2. Related Background Art
As a technique in such a field, one disclosed in Japanese Patent Application Laid-Open No. 7-326324 has conventionally been known. In the gas discharge tube described in this publication, a sealed envelope is constituted by a side tube made of glass and a stem made of glass, and anode and cathode sections are secured to the upper ends of the stem pins, respectively. Also, the anode and cathode sections are contained in a cylindrical light-emitting part assembly, which has a floating structure in a state spaced from the stem, and each stem pin is surrounded by an electrically insulating pipe such that the stem pins are not exposed between the light-emitting part assembly and the stem. In order for the gas discharge tube to be utilized as a UV light source, the sealed envelope is filled with about several Torr of deuterium gas.
Since the conventional gas discharge tube is configured as mentioned above, however, there have been problems as follows.
Namely, while the light-emitting part assembly is supported by a plurality of stem pins, a floating structure including electrically insulating pipes interposed therein is employed, whereby it is hard to secure a resistance to vibration, and its use may be restricted.
In order to overcome the above-mentioned problems, it is an object of the present invention to provide a gas discharge tube having an improved resistance to vibration, enhancing the heat-radiating characteristic of the anode section, and facilitating the easiness in assembling.
For overcoming the above-mentioned problems, the gas discharge tube in accordance with the present invention is a gas discharge tube having a sealed envelope at least a part of which transmits light. The sealed envelope is filled with a gas and is provided with anode and cathode sections disposed therein. The electric discharge is generated between the anode and cathode sections, so that the light-transmitting part of the sealed envelope emits predetermined light outside. The sealed envelope comprises of a stem for securing the anode and cathode sections by way of respective stem pins independent from each other, a side tube, made of a material at least a part of which transmits light and secured to the stem, surrounding the anode and cathode sections, and an anode support plate abutting against the stem so as to support the anode section on a surface thereof.
Though this gas discharge tube generates a high heat in the anode section while in use, it employs a configuration in which the anode support plate abuts against the stem, whereby the heat is transmitted to the stem by way of the anode support plate and is released outside by way of the stem. As a consequence, the cooling efficiency of the anode section can be improved, which contributes to improving the stabilization of operation characteristics. Also, since the anode section employs not a floating structure including stem pins interposed therein but a configuration in which the anode section is seated on the stem in a state where the support plate is interposed, the anode section is stabilized, and the resistance to vibration is improved. For assembling the anode section into the sealed envelope, it will be sufficient if the anode support plate is simply mounted on the stem, which contributes to improving the easiness in assembling as well.
Preferably, the anode support plate may be made of an electrically insulating material. When such a configuration is employed, the anode support plate can appropriately electrically block the anode section and the stem from each other.
Preferably, the anode support plate may be provided with a cavity portion for containing the anode section. In this case, the anode section is contained within the cavity portion of the anode support plate, so that the anode section can stably be seated in the anode support plate, and the wall face forming the cavity portion can surround the anode section, whereby the electric shield effect can be improved.
It may further comprise a spacer plate made of ceramics, in contact with an exposed surface of the anode support plate with the anode section interposed therebetween, having an opening for exposing the anode section; and an electrically conductive focusing electrode plate, in contact with a surface of the spacer plate, having a focusing opening disposed coaxial with the opening of the spacer plate, the cathode section being secured within the sealed envelope so as to be spaced from the focusing electrode plate.
When such a configuration is employed, it will be sufficient if the anode support plate, the anode section, the spacer plate, and the focusing electrode plate are successively stacked on the stem within the sealed envelope, whereby each component within the sealed envelope is stabilized, and stable mass production is facilitated in the making of the gas discharge tube.
Preferably, it further comprises a cover plate secured to the focusing electrode plate so as to face a light projection window disposed at an upper part of the side tube and cover the upper side from the cathode section. When such a configuration is employed, the cover plate functions as a shield plate, whereby the sputtering materials or evaporated materials released from the cathode section are blocked by the cover plate and thus become harder to attach to the light projection window.
Preferably, a body of the side tube in the sealed envelope is formed from a metal. When such a configuration is employed, the side tube is easily formed by pressing, which facilitates mass production.
Preferably, the stem is provided with a first flange portion made of a metal, the side tube is provided with a second flange portion made of a metal, and the first and second flange portions are secured to each other by welding. In the case where such a configuration is employed, when the first flange portion provided in the stem and the second flange portion provided in the side tube are aligned face to face, the operation of joining the metals to each other becomes easier, so that the welding operation such as electric welding, laser welding, or the like becomes reliable, which facilitates mass production.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.